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Spinosaurus ("spine lizard") is a genus of large, carnivorous theropod dinosaurs known from mid-Cretaceous Africa, with most material referred to the creature having come from Egypt and Morocco. They were among the largest theropod dinosaurs to have ever lived.

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Description

The most notable feature of Spinosaurus was a row of tall spines that adorned its back, which are believed to have supported a sail in life, not unlike Ouranosaurus and the non-dinosaur Dimetrodon. It has been theorized that this "sail" would have been used for display purposes, to attract mates and intimidate rival spinosaurs.

Spinosaurus, like its relatives Baryonyx and Suchomimus, had sleek jaws like those of species of long snouted crocodilians (such as orinoco crocodiles and Australian freshwater crocodiles) and gharials, along with a long neck, both adaptions suited for seizing aquatic prey, which comprised a part of their diets (evidence exists that suggests spinosaurids also ate other animals, including pterosaurs and other dinosaurs).

Spinosaurus, as it was commonly depicted prior to 2014

Also like Baryonyx and Suchomimus, it bore massive, hook-like claws on its hands.

Size

Spinosaurus is estimated to have been able to reach lengths of up to 15 - 16 meters (50 - 52 feet) from large specimens,[1] making it the longest carnivorous dinosaur known, even longer than Tyrannosaurus and Giganotosaurus - some extreme estimates from prior to 2014 suggested that it could reach lengths of nearly 18 meters (60 feet). However, it was likely not as tall as the two creatures if its legs were as short as what was proposed by Ibrahim et al.. Modern estimates for the weight of larger Spinosaurus place them around 6.5 - 7.5 tons,[1] lighter than some species other theropods of similar length. Earlier weight estimates range between 6 (lighter than most Tyrannosaurus estimates) and 23 short tons (exceedingly unlikely given how light the dinosaur's build was, and much heavier than all known predatory dinosaur estimates and some species of sauropods).

Legs

Life restoration of Spinosaurus in an aquatic environment

In 2014, material was described revealing that its legs were much shorter than those of its relatives, to such a degree that some have proposed that it was restricted to a quadrupedal gait when on land; others have suggested that it assumed a stance not unlike that of a pangolin. The find and the Spinosaurus specimen in question (named FSAC-KK 11888) have been questioned - some have proposed that the legs belong to a younger Spinosaurus than the rest of the specimen in the Ibrahim study (which would mean that it is chimeric, a mix of separate spinosaurs). Regardless of whether or not FSAC-KK 11888 is a chimera, Spinosaurus still would have had significantly proportionately shorter legs than its relatives in life.

Paleobiology

Many have suggested that several of Spinosaurus's anatomical traits, including its unusually small hind legs and its possibly-webbed feet, were adaptations for swimming in deep water, a suggestion bolstered by the description of a Spinosaurus tail, which was thin, flexible and bore a "sail", and would very likely have been used as a means of propulsion like the tail of a crocodilian.[2][3]

However, a bioisotope analysis done by Romain Amiot and colleagues found that oxygen isotope ratios of spinosaurid bones indicate differentiated habitat preferences for spinosaurid species. Isotope ratios from teeth from Baryonyx, Irritator, Siamosaurus, and Spinosaurus were compared with isotopic compositions from contemporaneous theropods, turtles, and crocodilians; the study concluded that the Siamosaurus specimens tended to have the largest difference from the ratios of other theropods, and Spinosaurus tended to have the least difference. [4]

Spinosaurus, as it is depicted in The Land Before Time Animated Moviebook

Outside of The Great Day of the Flyers, Spinosaurus also makes a small appearance in The Land Before Time Animated Moviebook during a minigame, wherein it is depicted similarly to how it was often depicted in the late 1980's and early 1990's.